Research subject: In this study, Fe₃O₄ nanoparticles were first synthesized through a controlled co-precipitation method. Subsequently, a uniform silica coating was formed on the surface of iron oxide nanoparticles via the Stöber process using tetraethyl orthosilicate (TEOS) as the silica precursor, resulting in core–shell Fe₃O₄@SiO₂ nanoparticles with a stable and well-organized structure. The obtained nanoparticles were then functionalized with a molecularly imprinted polymer (MIP) to produce a targeted and selective adsorbent for the removal of zinc ions (Zn²⁺) from aqueous solutions. The concentration of Zn²⁺ ions was determined using Inductively Coupled Plasma (ICP) analysis.
Research approach: To comprehensively investigate the physical, chemical, and structural characteristics of the synthesized nanoadsorbent, various analytical techniques were employed, including transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), dynamic light scattering (DLS), vibrating sample magnetometry (VSM), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR).
Main results: The characterization results confirmed the formation of a coherent structure with uniform particle size distribution, good thermal stability and successful incorporation of active functional groups on the nanoparticle surface. The adsorption performance of the nanoadsorbent for Zn²⁺ ions was evaluated by studying the effects of various operational parameters, including adsorbent dosage, contact time, pH and initial metal ion concentration. Optimized results revealed that under the conditions of an adsorbent dosage of 16 mg, pH=7, an initial concentration of 0.45 mmol L⁻¹, a solution volume of 50 mL, and a contact time of 21 min, the removal efficiency of Zn²⁺ ions reached 96%, indicating the high performance of the adsorbent (107.55 mg/g). Also, isotherm studies demonstrated that the adsorption process followed the Langmuir model, suggesting a monolayer adsorption mechanism. Furthermore, kinetic analysis showed that the experimental data fitted the pseudo-second-order model, confirming that chemisorption was the dominant rate-controlling mechanism. In addition, the synthesized nanoadsorbent exhibited excellent magnetic separability, allowing for easy recovery from the aqueous solution. It also demonstrated high reusability over multiple adsorption-desorption cycles without significant loss in its adsorption performance. Therefore, the designed adsorbent can be considered a stable, efficient, and environmentally friendly system, offering a promising approach for the effective treatment of industrial wastewater containing heavy metal ions.